Conventional techniques for fabricating an integrated-circuit (IC) die rely on a single lithography cycle to pattern oxide gates of device transistors of the IC die. This results in device transistors of the IC die having oxide gates with a similar thickness, which governs device functionality and performance over a particular voltage range. In some cases, however, the device transistors of the IC die are configured to support multiple types of devices that operate at different respective voltage levels, such as memory devices, processor core devices, input/output (I/O) devices, and the like. To ensure correct operation of the multiple types of device transistors at different respective voltage levels, IC dies often include additional circuitry for voltage regulation or isolation to prevent lower-voltage transistor devices from being damaged by high voltage signals of other device types. The addition of this regulation and protection circuitry, however, can be expensive in terms of power, circuit complexity, or design space of an IC die.